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Anglers in eastern Lake Ontario want to kill hungry cormorants to stop them eating so many fish. That theory wouldn't hold much water in these parts, say researchers, because Hamilton Harbour cormorants don't actually like popular sport species.

The 3,500 pairs that nested around Burlington Bay last year chowed down on smelt, alewives and round gobies, not trout, perch and bass, study shows.

McMaster biology professor Jim Quinn and his students went to great lengths to determine what the sleek black birds eat -- they examined almost 11 kilograms of cormorant vomit, he said at a weekend workshop held by the Bay Area Restoration Council.

"You palpate the abdomens of chicks and identify what they upchuck."

The stomachs of 275 chicks contained mostly alewives, followed by gobies, smelt and sticklebacks. There was only one salmonid (salmon or trout) and a few pumpkinseeds (sunfish with orange bellies).

Quinn says those who blame cormorants for taking too many desirable fish "might want to point their fingers back in the direction of humans."

When an audience member asked Quinn about cormorant feces killing the trees in which they nest, he said we may have to accept it, though removing some nests and other "relatively benign management might be in order."

He reported the rapid rise in cormorant numbers appears to be levelling off and said the population may be reaching the area's natural capacity to support the species.

If that's the case, he said, culling or reducing numbers will only cause the birds to reproduce more rapidly.

Katie Fernandes, chair of Hamilton's wildlife management advisory committee, says efforts to reduce the number of ring-billed gulls and Canada geese will continue because their droppings are polluting beaches.

Goose eggs are oiled to prevent them hatching. Noisemakers and captive eagles or other birds of prey are used to scare gulls away from nest sites.